Nebuchadnezzar was actually Belshazzar’s grandfather, not his “father” (v. 2), but Daniel was writing in Chaldean, and there was no Chaldean word for grandfather, nor any Hebrew word for it (cf. II Sam. 9:6, 7) or Greek word (cf. Mt. 1:1).
Belshazzar asked to drink out of the vessels from Israel’s temple (v. 2, 3) to show his contempt for Israel’s God. So God allowed him to be conquered by the Medes and Persians (Jer. 51:37-39; 51:57, 58) later that night (Dn. 5:30, 31).
Daniel 5:5 mentions the hand’s “fingers” because back then “the finger of God” was a figure of speech that meant God must have His finger in something (Ex. 8:18). But in the Bible, “the finger of God” was a symbol of “the Spirit of God” (Mt. 11:28 cf. Lu. 11:20). God’s Spirit wrote the law (Deut. 9:10) and the rest of the Word of God (II Pe. 1:20, 21).
The Spirit wrote on the wall by “the candlestick” (Dan. 5:5) the king probably also got from the temple (Jer. 52:12-19). God predicted the king’s fear 100 years earlier (Isa. 21:2-4).
Belshazzar could only offer his wise men “third” place in the kingdom because his father Nabonidus was actually the king; he was just out of town. That made Belshazzar himself second in the kingdom, so he couldn’t offer that position as a reward as Pharaoh did for Joseph (Gen. 41:42).
Belshazzar’s wise men couldn’t interpret the writing (cf. Isa. 44:24, 25) for it was God’s Word, and unsaved men can’t understand the Word (I Cor. 2:14). Only a man with the Spirit can, something we see symbolized by the way God laid out the temple. The bread on the table of showbread had two rows of six loaves (Lev. 24:5, 6) to represent the Bible’s 66 books, for man doesn’t live by bread alone, but by every word that proceeds from God’s mouth. God parked that bread under the candlestick that represents the Spirit to symbolize that only He can shed “light” on God’s Word.
The queen heard the king’s fear and came in (5:9, 10). She must have been his mother, for “all” his wives were already at the party (5:2). She told him to call Daniel in to interpret the writing (5:11-17). Daniel refused the king’s offer to be Babylon’s 3rd ruler, even though he accepted a reward from his grandfather (Dan. 2:48), because he knew Babylon would fall that night and most of her rulers would likely be killed. Besides, he had all the “chains” (5:16) he needed (Pr. 1:7-9).
After Daniel reminded the king that pride had been his grandfather’s downfall (5:18-25), he began to interpret his dream. “Mene” (v. 26) means numbered and, being a prophet, Daniel amplified it to mean God had numbered the years of his kingdom to be 70 years (Jer. 25:11, 12), and his number was up! “Tekel” (Dan. 5:27) means weighed, which Daniel amplified to mean he’d been weighed and found wanting. “Peres” (v. 28) was a form of “upharsin” and meant his kingdom would be “divided” to the combined kingdom of Media-Persia. God predicted this 100 years ealier and said they couldn’t be bribed to not conquer them (Isa. 13:1, 17).
Daniel eventually had to accept a position as 3rd ruler because the king “commanded” it (Dan. 5:29), and God’s people are supposed to do what the king commands. Besides, he just got done acting like the 3rd person in God’s kingdom, the Spirit, when he interpreted the Word of God. Joseph was a type of Christ, the 2nd person in the Trinity, so God allowed him to be made the 2nd ruler in Egypt.
God sketched out how Babylon would fall (Isa. 21:4-9), but didn’t give the full story that history gives us. History says the Medes and Persians dammed up the Euphrates River that ran through Babylon, allowing them to sneak in under the massive walls. Belshazzar and all his rulers were too drunk to fight them off, or even believe the initial reports that the wall had been breached.
Why wouldn’t God include that great story in the Bible? Because Babylon will rise and fall again, and this fall is a type of that fall, and God didn’t want you to think future Babylon will fall the same way, for it will burn (Rev. 18). Future Babylonians will be saying “peace and safety,” just as they did in ancient Babylon, but destruction will fall on them just as suddenly (I Thes. 5:3) “in one hour” (Rev. 18:10).